Optical Sheet, and Backlight Unit and Display Using the Same

ABSTRACT

In an optical sheet which is used for light control illumination in a backlight unit for a display, in order from an incident side of an illuminating light, there are provided at least a light scattering layer which scatters the illuminating light toward an outgoing surface side, an adhesion layer or an adhesive layer, a light reflection layer which reflects light scattered by the light scattering layer toward the light scattering layer side, and a lens sheet whose flat rear face is fixed to the other side of the light reflection layer, and in which a plurality of unit lenses are disposed on the surface. Opening portions corresponding to the respective unit lenses one-to-one are provided to the light reflection layer, and thickness of the adhesion layer or the adhesive layer is thinner than that of the light reflection layer.

CROSS-REFERENCE TO RELATED APPLICATIONS

This is application is a continuation of U.S. application Ser. No.11/808,120 filed Jun. 6, 2007, which is a Continuation Application ofPCT Application No. PCT/JP2006/301572, filed Jan. 31, 2006, which waspublished under PCT Article 21(2) in Japanese, the entire contents ofall are incorporated herein by reference. This application is also basedupon and claims foreign priority benefit from prior Japanese PatentApplication No. 2005-022936, filed Jan. 31, 2005, the entire contents ofwhich is incorporated herein by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to an improvement of an optical sheet usedfor controlling an illumination light path mainly in a backlight unitfor a display which uses a liquid crystal display element, and inparticular, to a backlight unit and a display which are equipped withthe optical sheet.

2. Description of the Related Art

As displays which are typified by liquid crystal displays, thepopularization of a type in which a light source required forrecognizing presented information is built in has been remarkable. In abattery-powered device such as a laptop computer, the electric powerconsumed by the light source accounts for a considerable percentage ofthe electric power consumed in the entire battery-powered device.

Accordingly, the battery life is increased by reducing the totalelectric power required for providing a predetermined luminance. This isparticularly favorable for a battery-powered device.

The Brightness Enhancement Film (BEF) which is a registered trademark ofa U.S. company, 3M, has been broadly used as an optical sheet forsolving this problem.

As shown in FIG. 1, the BEF is a film in which unit prisms 72 having atriangular-shaped cross section are arrayed periodically in onedirection on a single component 70.

The unit prisms 72 have sizes (a pitch) which are larger than awavelength of light.

The BEF condenses “off-axis” light and redirects it “on-axis” toward aviewer or recycles the light.

At the time of using the display (turn on), the BEF increases theon-axis luminance by reducing the off-axis luminance. The term “on-axis”here is a direction coincident with a visual direction of a viewer, andis generally along a normal line direction with respect to a displayscreen (the direction F shown in FIG. 1).

When the repeating array structure of the unit prisms 72 is a parallelstructure in only one direction, it is possible to only redirect orrecycle light in the parallel direction, and in order to carry outluminance control of a display light in horizontal and verticaldirections, two sheets are used in combination so as to be superimposedon one another such that the parallel directions of the prism groups aresubstantially perpendicular to one another.

In accordance with such use of the BEF, it is possible for a displaydesigner to achieve a desired on-axis luminance while reducing anelectricity consumption.

As Patent Documents which disclose a technology of using a luminancecontrol component having a repeating array structure of the unit prisms72 typified by the BEF, for a display, there have been a number ofPatent Documents, as shown by, for example, Jpn. Pat. Appln. KOKOKUPublication No. 1-37801, Jpn. Pat. Appln. KOKAI Publication Nos.6-102506 and 10-506500.

In an optical sheet using the BEF as a luminance control component asdescribed above, as shown in FIG. 2, it is possible to control so as toenhance a light intensity in the visual direction F of a viewer byemitting a light beam L from a light source 20 finally at a controlledangle φ by refraction x. However, at the same time, optic elements dueto reflection/refraction Y are emitted wastefully in a cross directionwithout heading in the visual direction F of a viewer.

Accordingly, in a light intensity distribution emitted from the opticalsheet using the BEF as shown in FIG. 1, as shown in the light intensitydistribution B of FIG. 3, the light intensity in the visual direction Fof the viewer, i.e., at an angle 0° with the visual direction F isenhanced to the maximum. However, as shown by small light intensitypeaks in the vicinity of ±900 shown on the abscissa in the drawing,there is the problem that light emitted wastefully from cross directionsis increased.

Further, when the above-described component 70 is used for a direct-typesystem backlight unit in which an optical waveguide structuring anedge-light type surface light source is not used, a structure in which alight diffusion layer (a single light diffusion plate or a combinationwith a light diffusion film) is placed between the light source 20 andthe component 70 is commonly used. However, due that their surfaces areflat, when both components are in contact (the component 70 and thelight diffusion layer (not shown)) such that there is not a definiteboundary surface and if both are materials having a refractive indexclose to one another, the light incident on the unit prisms 72 is notincident at the intended angle, which makes it difficult to perform theoptical characteristic as designed by the unit prisms 72.

In particular, in the case of using a structure in which the component70 and the light diffusion layer are laminated to be integrated via anadhesive layer or an adhesion layer, generation of unexpected elementsof incident light (or a reduction in functions due to the lightdiffusion layer) is easily brought about, which makes it furtherdifficult to perform the optical characteristic as designed.

The present invention has been achieved in consideration of thecircumstances, and an object of the present invention is to provide anoptical sheet in which it is possible to emit light from a light sourceso as to be uniformed, and to control a diffusion range withoutincreasing an amount thereof emitted wastefully.

Note that, in the present application, “diffusion” and “scattering”serving as an optical characteristic, “adhesion layer” and “adhesivelayer”, and “optical sheet” and “optical film” according to the presentapplication are used as synonyms.

BRIEF SUMMARY OF THE INVENTION

In order to achieve the above-described object, in the presentinvention, the following measures are devised.

Namely, an optical sheet according to a first aspect of the presentinvention, which is used for light control illumination in a backlightunit for a display, has light reflection parts at non-light condensingareas by the lens unit, and light transmission parts at areas other thanthe light reflection parts, on the surface opposite to the lens unit ofa lenticular sheet having lens units. The lenticular sheet having lensunits is formed such that a convex cylindrical lens group is formed inparallel on one side.

The light reflection parts are formed by applying coating formation andtransferring formation of an ink layer formed by dispersive mixingfiller metal, or by laminating formation of metallic foil.

The light transmission parts need not be flat surfaces, and could beconvex portions or concave portions formed on the surfaces.Alternatively, at least one of convex cylindrical lenses and concavecylindrical lenses may be formed on the light transmission parts.

Based on a distance TB measured from a valley portion of the concavityand convexity structuring the lens unit to the surface on the otherside, a width A of the light transmission parts, a pitch P between theparallel convex cylindrical lenses, and a critical angle α at theinterface of the lenticular sheet at the light transmission parts, arelation of P≦A+2*TB*tan α is formed.

Further, based on a height TL of the concavity and convexity structuringthe lens unit, a distance TB from a valley portion of the concavity andconvexity to the surface on the other side, a width A of the lighttransmission parts, and a pitch P between the parallel convexcylindrical lenses, relations of0.3<TL/P<0.6,0.3<TB/P<1.0, and0.3<A/P<0.6are formed.

Further, the lenticular sheet is formed from a laminated structure inwhich the lens unit is formed on one surface of a sheet-like transparentbase material, and at the boundary of unit lenses adjacent to oneanother, a tangent line at a valley portion of the adjacent unit lensesis within a range of 35 to 600.

On the other hand, the light reflection parts are, as one example, in astrip form having light transmission parts corresponding to therespective unit lenses which are convex cylindrical lenses one-to-one,and convex portions corresponding to the stripe form are formed on thesurface opposite to the lens unit.

Further, an optical sheet according to a second aspect of the presentinvention, which is used for light control illumination in a backlightunit for a display, has, in order from an incident side of anilluminating light: a light scattering layer which scatters theilluminating light toward an outgoing surface side serving as anon-incident surface side; an adhesion layer or an adhesive layer; alight reflection layer which is made to adhere or stick to the lightscattering layer by the adhesion layer or the adhesive layer, which hasa surface with high light reflectivity so as to face the outgoingsurface side of the light scattering layer, and which reflects lightscattered by the light scattering layer toward the light scatteringlayer side; and a lens sheet whose flat rear face is fixed to the otherside of the light reflection layer, and in which a plurality of unitlenses are disposed on a surface. The light scattering layer may be adiffusion sheet using a general base material typified by, for example,PET (polyethylene terephthalate), PC (polycarbonate), PMMA (polymethylmethacrylate), PP (polypropylene), PE (polyethylene), or may be adiffusion plate using a base material typified by PC, PMMA, acryl, PS(polystyrene). Then, opening portions respectively corresponding to theunit lenses one-to-one are provided to the light reflection layer, and athickness of the adhesion layer or the adhesive layer is thinner thanthe light reflection layer.

Moreover, the lens sheet is a lenticular sheet having a lens unit formedsuch that semi-tubular convex cylindrical lenses are arranged as unitlenses in parallel in one direction. When parallel light beams are madeincident onto the lenticular sheet from the lens unit side, by providingstriped portions of light-transmitting openings serving as openingportions so as to include areas onto which the incident parallel lightbeams are condensed by the focusing action of the lens unit, non-openingportions are formed from a stripe-form light reflection layer, and apitch between the semi-tubular parallel convex cylindrical lenses and aformation pitch of the stripe-form opening portions are made equal. Theshapes of the unit lenses described as the semi-tubular convexcylindrical lenses may be of various types, such as spherical oraspherical, and as a height of the concavity and convexity of the lensunit, various designs may be used.

For example, the opening portions contacting the rear face of the lenssheet are air layers, or are formed from a material with a refractiveindex lower than that of the lens sheet. The adhesion layer or theadhesive layer is an ultraviolet curing resin layer, a pressuresensitive adhesive layer, a thermosensitive adhesion layer, or the like.Alternatively, this may be structured so as to include light diffusiblefine particles. The light reflection layer is white ink, metallic foil,metallized layer, or the like.

Such a lens sheet is a monolithic compact obtained by press molding orextrusion molding using, for example, thermoplastic resin. Further, sucha lens sheet has a laminated structure in which unit lenses formed fromhardened material of radiation cured resin, or thermoplastic resin areformed so as to polymerizing-adhere onto the surface of the basematerial.

Moreover, there may be provided a light scattering layer formed from asheet or a film having a light scattering characteristic, or areflective polarization split film on the light outgoing surface side ofsuch an optical sheet.

On the other hand, a third aspect of the present invention is abacklight unit for a display which is structured by providing such anoptical sheet on the back face of an image display element specifying adisplay image, along with a light source. Here, as a light source, forexample, a direct-type light source, a surface light source formed froman edge-light type light source and an optical waveguide, or the like isused.

Moreover, a fourth aspect of the present invention is a display in whichsuch a backlight unit for a display is structured by combining an imagedisplay element formed from a liquid crystal display element specifyinga display image in accordance with transmission/prevention oflight-transmittance in units of pixels, and a light source formed from acold-cathode tube or an LED.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING

FIG. 1 is a perspective view showing a structural example of a BEF.

FIG. 2 is a diagram for explanation of an optical effect of the BEF.

FIG. 3 is a chart showing a light intensity distribution with respect toangles with a visual direction of the BEF.

FIG. 4 is a side view showing one example of an optical sheet accordingto an embodiment of the present invention.

FIG. 5 is a plan view showing an example of a stripe form layout of alight reflection layer and opening portions.

FIG. 6 is a partial side view showing a detailed structural example ofthe optical sheet according to the embodiment.

FIG. 7 is a graph showing general relations among opening ratios,luminance, and visual field half-value angles.

FIG. 8 is a diagram for explanation of an optical effect of the opticalsheet according to the embodiment.

FIG. 9 is a chart showing light intensity distributions with respect toangles with a visual direction of the optical sheet according to theembodiment.

FIG. 10 is a conceptual diagram showing a structure of the backlight forperformance evaluation when the optical sheet according to theembodiment is applied to a backlight for a display.

FIG. 11 is a chart showing light intensity distributions in thebacklight to which the optical sheet according to Example 1 is applied.

FIG. 12A is a table in which concrete structures of respective parts inthe structure of the backlight for performance evaluation shown in FIG.10 are listed.

FIG. 12B is a table in which concrete structures of respective parts inthe structure of the backlight for performance evaluation shown in FIG.10 are listed.

DETAILED DESCRIPTION OF THE INVENTION

Hereinafter, best modes for carrying out the present invention will bedescribed with reference to the drawings.

FIG. 4 is a side view showing one example of an optical sheet accordingto an embodiment of the present invention.

Namely, an optical sheet 10 according to the present embodiment has alight diffusion layer 13 which conduct a light beam L from a lightsource 20 thereinto from an incident surface 11, and scatters the lighttoward an outgoing surface 12 side.

As the light diffusion layer 13, as is well known in the art, there isused a layer having a structure in which resin beads or fine particles(fillers) with different refractive indexes are included in transparentresin, or a layer having a structure whose one side is processed to havea mat shape.

Further, a light reflection layer 14 is fixed to the outgoing surface 12of the light diffusion layer 13 with an adhesion layer 18. The lightreflection layer 14 is formed from, for example, white ink, metallicfoil, or metallized layer, and as shown in the plan view of FIG. 5, hasprovided thereon a plurality of opening portions 15 formed from, forexample, regular air layers.

Moreover, the other surface of the light reflection layer 14 (the uppersurface of the light reflection layer 14 shown in FIG. 4) has fixedthereon a lens sheet 17 formed by disposing on its own surface aplurality of unit lenses 16.

As the adhesion layer 18, for example, an ultraviolet curing resin(hereinafter called “UV cure adhesive” as well) or another type ofadhesive is used, and there are cases in which a diffusing agent may bemixed thereinto in order to improve the diffusivity of the lightdiffusion layer 13. In consideration of the adhesive property left evenafter manufacturing the optical sheet 10, chances of bringing about areduction in durability characteristic or optical characteristic overtime are low. Thus, a polymerizing-adhesive strength changeable byultraviolet curing resin type is favorably used. Further, when theadhesion layer 18 formed from an ultraviolet curing resin is formed onthe entire surface of the lens sheet 17, provided that the adhesionlayer 18 is hardened, it is easy to prevent the portions not contactingthe light reflection layer 14 from being inserted into the openingportions 15, which is favorable.

FIG. 6 is a side view showing a structural example of the lens sheet 17.

In the example shown in FIG. 6, the lens sheet 17 has a lens unit inwhich the unit lenses 16 formed from semi-tubular convex cylindricallenses with a height TL are arrayed in parallel at a pitch P on one sidesurface, and has the light reflection layer 14 with high lightreflectivity which reflects toward the light source 20 side, on theother surface. In the light reflection layer 14, the opening portions 15formed from, for example, air layers with a width A corresponding to therespective unit lenses 16 of the lens sheet 17 one-to-one are disposedin a stripe form. Then, this is structured such that, in order for alight beam incident onto the opening portions 15 to be efficientlyincident to the semi-tubular convex cylindrical lenses, spaces betweenthe opening portions 15 and the semi-tubular convex cylindrical lensesare filled with a material with a refractive index n which is the sameas or close to that of the semi-tubular convex cylindrical lenses.

In the lens sheet 17 structured in this way, in order for a light beamto be efficiently incident onto the unit lenses 16 formed from thesemi-tubular convex cylindrical lenses, given that a distance from avalley portion between the unit lenses 16 up to the surface on the otherside is TB, a relation ofP≦A+2*TB*tan αis satisfied. In this formula, a is a critical angle at the interfacewith the lens sheet 17 in the opening portions 15, and is defined asα=sin⁻¹ (n₀/n) by using the refractive index n₀ of the opening portions15.

On the other hand, A/P corresponds to an opening ratio. However, asshown in FIG. 7, there is the general characteristic that the greaterthe opening ratio A/P is, the more the visual field half-value angle isimproved, but the luminance is lowered. Therefore, it is necessary toset the opening ratio A/P in consideration of a balance between theluminance and visual field half-value angle. Therefore, among a heightTL, a distance TB, a width A of the opening portion, and a pitch P,relations of0.3<TL/P<0.6  formula (1),0.3<TB/P<1.0  formula (2), and0.3<A/P<0.6  formula (2)are formed.

In the formula (1), when TL/P is less than or equal to 0.3, the focusingproperty of a lens is insufficient, and when TL/P exceeds 0.6, thedirectivity of the lens is too strong, which is not suitable for TV use,and molding thereof is made difficult.

In the formula (2), when TB/P is out of the above-described range, it isimpossible to efficiently guide the light to the lenses, which resultsin an increase in light quantity loss.

In the formula (3), when A/P is less than or equal to 0.3, thedirectivity is too strong, and absorption in a white reflection layerappears prominently, which results in an increase in light quantityloss. In contrast thereto, when A/P is greater than or equal to 0.6, thediffusion characteristic is too strong (the focusing property is weak),and it is difficult to improve the front surface luminance.

Further, a range of an angle θ formed with a boundary (valley portion)between the unit lenses 16 adjacent to one another is preferably from35° to 60° as will be described hereinafter.

Namely, when an angle θ formed with a boundary (valley portion) betweenthe unit lenses 16 adjacent to one another is less than 35°, themold-releasing property after molding is degraded, or it becomesimpossible to mold-release a molded item due to a tip of a metallic moldbeing bent by repeating molding. In addition, the life of the metallicmold tends to be shorter due to a tip of the metallic mold being damagedat the time of handling the metallic mold. Further, in order to broadenan orientation characteristic by the unit lenses 16, it suffices to makea curvature radius of a semi-tubular convex cylindrical lens smaller, orto design a cross-sectional shape thereof to be an aspherical (elliptic)shape. However, provided that an angle θ formed with a boundary (valleyportion) between the unit lenses 16 adjacent to one another is made lessthan or equal to 600, it is possible to realize a satisfactoryorientation characteristic.

On the other hand, when the above-described angle θ exceeds 60°, theshapes of the unit lenses 16 are made smooth. Thus, the lens function isdegraded, and the orientation angle is made narrow, which goes againstthe object of the present invention directed to improvement of the lightintensity in the visual direction of the viewer.

Note that the unit lenses 16 are not limited to the semi-tubular convexcylindrical lenses, and a lens sheet in which convex lenses are arrayedin two dimensions, a lenticular sheet having a lens unit in whichsemi-tubular convex cylindrical lenses are arranged as the unit lenses16 in parallel in one direction, and another lens sheet, do not deviatefrom the spirit of the present invention.

Such a lens sheet 17 is a monolithic compact molded by press molding orextrusion molding a thermoplastic resin which has been well known in theart, by using, for example, PET (polyethylene terephthalate), PC(polycarbonate), PMMA (polymethyl methacrylate), COP (cycloolefinpolymer), or the like. Alternatively, this may be formed by ultravioletcuring molding in which an ultraviolet curing resin is disposed on abase material such as PET (polyethylene terephthalate), PP(polypropylene), PC (polycarbonate), PMMA (polymethyl methacrylate), PE(polyethylene), or the like.

The opening portions 15 have refractive indexes lower than that of thelight diffusion layer 13 and the lens sheet 17, and are formed atpositions corresponding to each of the plurality of unit lenses 16.

The areas at which the opening portions 15 are formed are set such thatrespective lines, connecting the apexes of the respective unit lenses 16in the lens sheet 17 with centers G on the respective cross sectionsobtained when it is assumed that the planes of the light reflectionlayer 14 (the upper surfaces of the light reflection layer 14 shown inFIG. 4) of the respective opening portions 15 corresponding to therespective unit lenses 16 are cross sections, are substantiallyorthogonal to the planes of the light reflection layer 14 (the uppersurfaces of the light reflection layer 14 shown in FIG. 4).

In other words, the opening portions 15 are formed such that the centersG in cross sections of the respective opening portions 15 exist on thevertical lines made along the thickness direction of the optical sheet10 from the apexes of the respective unit lenses 16.

Alternatively, the light reflection layer 14 may be provided at areasincluding non-light condensing surfaces by the unit lenses 16, and theopening portions 15 may be provided at the areas other than the lightreflection layer 14. Note that not only the flat surfaces but alsoconvex portions or concave portions may be formed on the surfaces of theopening portions 15. In the case of convex shapes, the convex portionsare preferably made lower than the convex portions corresponding to thestripes in manufacturing.

As widths A of the opening portions 15 are made greater, scattered lightbeams which have not been sufficiently narrowed are incident onto theunit lenses 16. As a result, as described above, optic elements whichare not emitted in the visual direction F of a viewer are increased.

On the other hand, as the widths A of the opening portions 15 are madesmaller, only scattered lights which have been narrowed more evenly areincident onto the unit lenses 16, and as the case may be, unevenness inoutgoing light beams emitted from the unit lenses 16 is increased.

Accordingly, the shapes and the widths A of the opening portions 15 aredesign matters determined in accordance with the specifications requiredfor the optical sheet 10.

For example, in the case of using a lenticular sheet as described aboveas the lens sheet 17, when parallel light beams are incident from thelens unit side, by providing the light-transmitting stripe-form openingportions 15, for example, as air layers, so as to include the areas ontowhich the incident parallel light beams are condensed by the focusingaction of the lens unit, non-opening portions are formed from thestripe-form light reflection layer 14, and a pitch of the parallelsemi-tubular convex cylindrical lenses and a formation pitch of thestripe-form opening portions 15 may be made equal.

The light reflection layer 14, formed so as to be partially penetratedby the plurality of opening portions 15 regularly disposed as describedabove, is formed by use of a print method, a transfer method, aphotolithography method, or the like which has been well known in theart. Alternatively, the light reflection layer 14 is formed by applyingformation or transferring formation of an ink layer formed by dispersionmixing metallic filler, laminating formation of metallic foil, or thelike.

Alternatively, as one type of photolithography method, a so-called“self-alignment technique” by which areas at which the opening portions15 are formed are specified by utilizing the focusing property of lensesthemselves is used.

At the time of specifying the opening portions 15 by the self-alignmenttechnique, as shown in FIG. 4, in order for the opening portions 15corresponding to the respective unit lenses 16 to include the verticallines made from the apexes of the unit lenses 16 to the rear faces ofthe lens sheet 17, it is necessary to irradiate parallel light beamsonto the entire surface of the lens sheet 17 from the unit lenses 16side.

Further, there may be cases in which photosensitive resin layers used atthe time of the self-alignment technique are left on the openingportions 15 to be specified. However, in consideration of the opticalcharacteristic and the durability characteristic after manufacturing theoptical sheet 10, a photosensitive resin of a type in which thetransparency is maintained is favorably used, and a type whoserefractive index is lower than that of the lens sheet 17 (which is closeto that of the air for example) is more favorable.

Next, the effect of the optical sheet according to the above-describedexample structured as described above will be described by use of FIG.8.

Namely, in the optical sheet 10 according to the present embodiment, thelight L from the light source 20 is incident from the incident surface11 of the light diffusion layer 13. The light L incident onto the lightdiffusion layer 13 is randomly scattered here. Among the light beamsscattered in this way, only light beams γ having passed through theopening portions 15 are guided to the lens sheet 17.

Because the respective opening portions 15 are respectively provided soas to face the apexes of the respective unit lenses 16 provided to thelens sheet 17, only light beams narrowed by the corresponding respectiveopening portions 15 are guided to the respective unit lenses 16.

Namely, since only the light beams γ whose scattering angles arenarrowed are incident onto the respective unit lenses 16 due to therespective opening portions 15 functioning as slits, there are no lightbeams obliquely incident onto the unit lenses 16. Therefore, it ispossible to eliminate light beams emitted wastefully in a crossdirection that are not in the visual direction F of a viewer. On theother hand, light beams β which have not been able to pass through theopening portions 15 are reflected on the light reflection layer 14 to bereturned to the light diffusion layer 13 side.

Then, after the light beams β are scattered at the light diffusion layer13 in the same way, the light beams β become light beams γ whosescattering angles are narrowed, and the light beams γ pass through theopening portions 15 to be incident onto the unit lenses 16, and arediffused within predetermined angles φ by the unit lenses 16, andthereafter, the light beams β are emitted.

In this way, the light L from the light source 20 is scattered, only thelight beams γ whose scattering angles are narrowed can be incident ontothe unit lenses 16, and light beams which have not been able to beincident onto the unit lenses 16 can be reutilized so as to be notemitted wastefully. Therefore, it is possible to emit the light from thelight source 20 so as to control a diffusing range while improving theutilizing efficiency thereof.

In accordance therewith, as shown in FIG. 9, a light intensitydistribution A emitted from the optical sheet 10 according to thepresent embodiment is made to be a distribution in which the small lightintensity peaks in the vicinity of ±90° on the abscissa in the drawingas in the light intensity distribution B emitted from the optical sheetusing the BEF are eliminated, and it is possible to further enhance thelight intensity in the visual direction F of a viewer centering on 0°shown on the abscissa in the drawing.

Note that, in order to further control the light beams emitted from theunit lenses 16, there may be further provided a light scattering layerformed from a sheet or a film with a light scattering characteristic,and a reflective polarization split film (the both are not shown) at thelight outgoing surface side which is the upper side of the unit lenses16 in FIGS. 4 and 8.

Here, various concrete examples of the optical sheet according to theabove-described embodiment will be described.

EXAMPLE 1

On one surface of a PET film (75 μm thickness), a cylindrical lens groupof the unit lenses 16 with a radius of curvature of 100 μm, and a layoutpitch of 200 μm is formed from hardened material of acrylic ultravioletcuring resin.

As the light reflection layer 14, a white ink layer (15 μm thickness) isformed by the transferring method such that a ratio between the openingportions 15 and the light reflection layer 14 is made to be one-to-one.

At this time, P≦A+2*TA*tan α is satisfied, which leads toTL/P=0.31,TB/P=0.38, andA/P=0.5,and the optical sheet satisfies the aforementioned conditions of (1) to(3).

EXAMPLE 2

On one surface of a PET film (75 μm thickness), a cylindrical lens groupof the unit lenses 16 with a radius of curvature of 100 μm, and a layoutpitch of 200 μm is formed from hardened material of acrylic ultravioletcuring resin.

As the light reflection layer 14, a white ink layer (15 μm thickness) isformed by the transferring method such that a ratio between the openingportions 15 and the light reflection layer 14 is made to be one-to-one.

Further, as the adhesion layer 18, an acrylic pressure sensitiveadhesive material or a thermosensitive adhesive material (5 μmthickness) is formed, and is laminated with a PET film (75 μm thickness)which will be the light diffusion layer 13 to prepare the optical sheet10.

In this way, a thickness of the adhesion layer 18 is thinner than thatof the white ink layer serving as the light reflection layer 14.Accordingly, when the adhesion layer 18 is formed over the entiresurface of the lens sheet 17, it is possible to prevent the opticalcharacteristic from being affected on the basis of a difference betweenthe refractive indexes in accordance with the fact that the portions notcontacting the light diffusion layer 13 enter and fill up the openingportions 15.

EXAMPLE 3

On one surface of a PET film (75 μm thickness), a cylindrical lens groupof the unit lenses 16 with a radius of curvature of 100 μm, and a layoutpitch of 200 μm is formed from hardened material of acrylic ultravioletcuring resin.

As the light reflection layer 14, a white ink layer (15 μm thickness) isformed by the transferring method such that a ratio between the openingportions 15 and the light reflection layer 14 is made to be one-to-one.

Further, as the adhesion layer 18, an acrylic pressure sensitiveadhesive material or a thermosensitive adhesive material (5 μmthickness) to which 10% by weight of spherical-shaped acrylic resinfillers (average particle diameter 5 μm) serving as a diffusion materialis added is provided, and is laminated with a PET film (75 μm thickness)which will be the light diffusion layer 13 to prepare the optical sheet10.

In this case as well, in the same way as in example 2, a thickness ofthe adhesion layer 18 is thinner than that of the white ink layerserving as the light reflection layer 14.

EXAMPLE 4

On one surface of a PET film (75 μm thickness), a cylindrical lens groupof the unit lenses 16 with a radius of curvature of 100 μm, and a layoutpitch of 200 μm is formed from hardened material of acrylic ultravioletcuring resin.

As the light reflection layer 14, a white ink layer (15 μm thickness) isformed by the transferring method such that a ratio between the openingportions 15 and the light reflection layer 14 is made to be one-to-one.

Further, as the adhesion layer 18, a UV cure adhesive material (5 μmthickness) is provided, and is laminated with a PET film (75 μmthickness) which will be the light diffusion layer 13 to prepare theoptical sheet 10.

In this case as well, in the same way as in example 2, a thickness ofthe adhesion layer 18 is thinner than that of the white ink layerserving as the light reflection layer 14.

EXAMPLE 5

On one surface of a PET film (75 μm thickness), a cylindrical lens groupof the unit lenses 16 with a radius of curvature of 100 μm, and a layoutpitch of 200 μm is formed from hardened material of acrylic ultravioletcuring resin.

As the light reflection layer 14, a white ink layer (15 μm thickness) isformed by the transferring method such that a ratio between the openingportions 15 and the light reflection layer 14 is made to be one-to-one.

Further, as the adhesion layer 18, a UV cure adhesive material (5 μmthickness) to which 10% by weight of spherical-shaped acrylic resinfillers (average particle diameter 5 μm) serving as a diffusion materialis added is provided, and is laminated with a PET film (75 μm thickness)which will be the light diffusion layer 13 to prepare the optical sheet10.

In this case as well, in the same way as in example 2, a thickness ofthe adhesion layer 18 is thinner than that of the white ink layerserving as the light reflection layer 14.

EXAMPLE 6

On one surface of a PET film (75 μm thickness), a cylindrical lens groupof the unit lenses 16 with a radius of curvature of 100 μm, and a layoutpitch of 200 μm is formed from hardened material of acrylic ultravioletcuring resin.

As the light reflection layer 14, a white ink layer (15 μm thickness) isformed by the transferring method such that a ratio between the openingportions 15 and the light reflection layer 14 is made to be one-to-one.

Further, as the adhesion layer 18, an acrylic pressure sensitiveadhesive material or a thermosensitive adhesive material (5 μmthickness) is provided, and is laminated with a diffusion film (100 μmthickness, haze factor 90%, transmission factor 90%) which will be thelight diffusion layer 13 to prepare the optical sheet 10.

In this case as well, in the same way as in example 2, a thickness ofthe adhesion layer 18 is thinner than that of the white ink layerserving as the light reflection layer 14.

EXAMPLE 7

On one surface of a PET film (75 μm thickness), a cylindrical lens groupof the unit lenses 16 with a radius of curvature of 100 μm, and a layoutpitch of 200 μm is formed from hardened material of acrylic ultravioletcuring resin.

As the light reflection layer 14, a white ink layer (15 μm thickness) isformed by the transferring method such that a ratio between the openingportions 15 and the light reflection layer 14 is made to be one-to-one.

Further, as the adhesion layer 18, an acrylic pressure sensitiveadhesive material or a thermosensitive adhesive material (5 μmthickness) to which 10% by weight of spherical-shaped acrylic resinfillers (average particle diameter 5 μm) serving as a diffusion materialis added is provided, and is laminated with a diffusion film (100 μmthickness, haze factor 90%, transmission factor 90%) which will be thelight diffusion layer 13 to prepare the optical sheet 10.

In this case as well, in the same way as in example 2, a thickness ofthe adhesion layer 18 is thinner than that of the white ink layerserving as the light reflection layer 14.

EXAMPLE 8

On one surface of a PET film (75 μm thickness), a cylindrical lens groupof the unit lenses 16 with a radius of curvature of 100 μm, and a layoutpitch of 200 μm is formed from hardened material of acrylic ultravioletcuring resin.

As the light reflection layer 14, a white ink layer (15 μm thickness) isformed by the transferring method such that a ratio between the openingportions 15 and the light reflection layer 14 is made to be one-to-one.

Further, as the adhesion layer 18, a UV cure adhesive material (5 μmthickness) is provided, and is laminated with a diffusion film (100 μmthickness, haze factor 90%, transmission factor 90%) which will be thelight diffusion layer 13 to prepare the optical sheet 10.

In this case as well, in the same way as in example 2, a thickness ofthe adhesion layer 18 is thinner than that of the white ink layerserving as the light reflection layer 14.

EXAMPLE 9

On one surface of a PET film (75 μm thickness), a cylindrical lens groupof the unit lenses 16 with a radius of curvature of 100 μm, and a layoutpitch of 200 μm is formed from hardened material of acrylic ultravioletcuring resin.

As the light reflection layer 14, a white ink layer (15 μm thickness) isformed by the transferring method such that a ratio between the openingportions 15 and the light reflection layer 14 is made to be one-to-one.

Further, as the adhesion layer 18, a UV cure adhesive material (5 μmthickness) to which 10% by weight of spherical-shaped acrylic resinfillers (average particle diameter 5 μm) serving as a diffusion materialis added is provided, and is laminated with a diffusion film (100 mthickness, haze factor 90%, transmission factor 90%) which will be thelight diffusion layer 13 to prepare the optical sheet 10.

In this case as well, in the same way as in example 2, a thickness ofthe adhesion layer 18 is thinner than that of the white ink layerserving as the light reflection layer 14.

Next, the performance, exhibited when the optical sheets 10 according tothe above-described examples 1 to 9 are applied to a backlight unit fora display in a 26-inch liquid crystal television, was evaluated. Asconditions for the evaluation, a television structure formed from acold-cathode tube, an optical sheet group, and a liquid crystal panel isused, and a distribution of visual field angles of display luminance isevaluated sequentially by the following factors as the optical sheetgroup by use of a luminance meter (EZlite manufactured by Eldim).

When a BEF, manufactured by the U.S. 3M company is used as a brightnessenhancement film, generally, a structure as shown in FIG. 10 is used. Asfunctions of the respective parts, the diffusion plate has an effect ofeliminating a shadow of the light source by diffusing a light beam fromthe light source, and serves as a base for laminating various opticalfilms thereon. The lower diffusion film has a function of diffusing whenonly the diffusion by the diffusion plate is insufficient, and thereflective polarization split film is, for example, generally a DBEFserving as a reflective polarizing film manufactured by the U.S. 3Mcompany, and has an object to reflect and reutilize a polarized beam tobe eliminated by nature through a polarizing film laminated onto aliquid crystal panel. Further, as regards the characteristic of visualfield angles of luminance of the BEF, wasteful emission of light in across direction is reduced as shown in FIG. 11 by the DBEF function.

Note that the luminance distribution chart shown in FIG. 11 showsluminance distributions of light with a specific polarization component,and shows that a quantity of light with a component of a polarizationaxis passing through a polarization element on the lower side of theliquid crystal layer of a quantity of light from the backlight incidentonto the liquid crystal element rises by use of the DBEF.

The “upper diffusion film” and “lower diffusion film” in the concretecomparative structures shown in FIGS. 10, 12A, and 12B, and theembodiment have directivities in light scattering (diffusion), whichshows that there is a difference in the characteristics: there are manyscatter-emitting components in the upper direction or in the lowerdirection of the screen in an incident light beam.

Specifications of the respective films are as follows.

Lower diffusion film 1: film thickness 2 mm, haze factor 95%,transmission factor 80%.

Lower diffusion film 2: film thickness 100 μm, haze factor 90%,transmission factor 90%.

Lower diffusion film 3: film thickness 100 μm, haze factor 40%,transmission factor 90%.

Evaluation for image on the display has been carried out under theabove-described comparative structures and the example structures.

Note that the diffusion plate has an effect of diffusing light in thesame way as a diffusion film. However, in contrast to the fact that thediffusion film is structured so as to be flexible on a thin film, thediffusion plate is formed by extrusion molding, and has a thicknesslarger than that of the diffusion film, and a high rigidity.

In this way, it is necessary to use many optical films in a generalstructure. However, the optical sheet according to the first aspect ofthe present invention is designed so as to hardly produce any wastedoutgoing light in a cross direction even in a state in which there is noreflective polarization split film as in FIG. 11. Therefore, even whenthe reflective polarization split film is replaced with a normaldiffusion film, or is removed, the optical characteristic is notdeteriorated.

Further, in the optical sheet according to the second aspect of thepresent invention, even when the diffusion plate and the lower diffusionfilm are removed, the optical characteristic is not deteriorated.

Accordingly, the invention is highly effective in terms of, not only theoptical characteristic, but also a reduction in the number ofcomponents.

The optical sheet according to the embodiment of the present inventionas described above is effective not only in the case of application to aliquid crystal television with a relatively large screen having adirect-type light source, but also in the case of application to amedium with a small-scale display having a backlight unit with anedge-light type light source, or a light source formed from acold-cathode tube or an LED, and a waveguide plate.

1. An optical sheet for use in illumination light control in a backlightunit for a display, comprising: a light diffusion layer which diffusesillumination light toward an emission surface side of the lightdiffusion layer, which is a non-incidence surface side thereof; anadhesion layer or an adhesive layer; a light reflection layer which isadhered to the light diffusion layer by the adhesion layer or theadhesive layer, which has a front surface extending along the emissionsurface side of the light diffusion layer, and having a highreflectivity with respect to the emission surface side of the lightreflection layer, and which reflects the light diffused by the lightdiffusion layer toward the light diffusion layer; and a lens sheethaving a flat reverse surface fixed to the other surface of the lightreflection layer, and a front surface on which a plurality of unitlenses are provided, wherein: the light diffusion layer, the adhesionlayer or the adhesive layer, the light reflection layer and the lenssheet are provided in this order from an incidence side of theillumination light; the light reflection layer includes opening portionswhich are formed therein in positions corresponding to those of the unitlenses, respectively; and the adhesion layer or the adhesive layer isthinner than the light reflection layer.
 2. The optical sheet accordingto claim 1, wherein: the lens sheet includes a lens unit wherein as theunit lens, semi-tubular convex cylindrical lenses are arranged inparallel, or convex lenses are two-dimensionally arranged; and the lightreflection layer is striped to have stripe opening portions having lighttransmission characteristics and including areas onto which parallellight beams incident from a lens unit-side onto the lens sheet arecondensed by a focusing action of the lens unit, and a pitch ofarrangement of the parallel semi-tubular convex cylindrical lenses isequal to a pitch of arrangement of the stripe opening portions.
 3. Theoptical sheet according to claim 1, wherein the light reflection layerhas convex portions formed on a surface of the light reflection layerlocated which is located opposite to the lens unit, the convex portionsbeing arranged in a stripe manner and located to correspond to the unitlenses of the convex cylindrical lenses, respectively.
 4. The opticalsheet according to claim 1, wherein the adhesion layer or the adhesivelayer is any of ultraviolet curing resin layer, a pressure sensitiveadhesive layer or a thermosensitive adhesive layer.
 5. The optical sheetaccording to claim 1, wherein the adhesion layer or the adhesive layercontains light diffusion fine particles.
 6. The optical sheet accordingto claim 1, wherein the light reflection layer is formed of any of whiteink, metallic foil or a metallized layer.
 7. The optical sheet accordingto claim 1, wherein the lens sheet is a monolithic compact formed bypress molding or extrusion molding using a thermoplastic resin.
 8. Theoptical sheet according to claim 1, wherein the lens sheet has alaminated structure in which the unit lenses are formed of hardenedmaterial of radiation hardening resin, and are polymerizing-adhered ontoa surface of a base material sheet.
 9. A backlight unit for a displaycomprising at least a direct-type light source and the optical sheetaccording to claim 1, on a back surface of an image display elementspecifying a display image.
 10. A backlight unit for a displaycomprising at least a surface light source and the optical sheetaccording to claim 1, on a back surface of an image display elementspecifying a display image, the surface light source comprising anedge-light type light source and a waveguide.
 11. A display comprising:an image display element which comprises a liquid crystal displayelement specifying a display image in accordance withtransmission/prevention of light-transmittance in units of one pixel; alight source which comprises a cold-cathode tube or an LED; and theoptical sheet according to claim
 1. 12. An optical sheet for use inillumination light control in a backlight unit for a display,comprising: a lenticular sheet including a lens unit in which a group ofconvex cylindrical lenses are formed in parallel with each other, andhaving a surface located opposite to the lens unit, wherein: lightreflection parts are provided at areas of the surface of the lenticularsheet, which are close to a focal point of the lens unit; lighttransmission parts are provided located at the other areas of thesurface of the lenticular sheet; and at the lenticular sheet, onboundaries between adjacent unit lenses, a tangent line at a valleyportion of any adjacent two of the unit lenses falls within a range of35 to 60°.
 13. The optical sheet according to claim 12, wherein thelight transmission parts are not flat, and have surfaces in which convexor concave portions are formed.
 14. The optical sheet according to claim12, wherein the light transmission parts contain at least convex orconcave cylindrical lenses formed therein.
 15. The optical sheetaccording to claim 12, wherein the light reflection portion is stripedto have convex portions at the surface located opposite to the lens unitand to corresponding unit lenses of the convex cylindrical lenses,respectively.
 16. The optical sheet according to claim 12, wherein thelens sheet is a monolithic compact formed by press molding or extrusionmolding using a thermoplastic resin.
 17. The optical sheet according toclaim 12, wherein the lenticular sheet has a laminated structure inwhich the lens unit is formed on a surface of a light-transmission basematerial formed in the shape of a sheet.
 18. The optical sheet accordingto claim 12, wherein each of the light reflection parts is formed byapplying formation or transferring formation of an ink layer formed bydispersively mixing filler metal, or laminating formation of metallicfoil.
 19. An optical sheet for use in illumination light control in abacklight unit for a display, comprising: a light diffusion layer whichdiffuses illumination light toward an emission surface side of the lightdiffusion layer, which is a non-incidence surface side thereof; anadhesion layer or an adhesive layer; a light reflection layer which isadhered to the light diffusion layer by the adhesion layer or theadhesive layer, which has a front surface extending along the emissionsurface side of the light diffusion layer, and having a highreflectivity with respect to the emission surface side of the lightreflection layer, and which reflects the light diffused by the lightdiffusion layer toward the light diffusion layer; and a lenticular sheetincluding a lens unit having a flat reverse surface fixed to the othersurface of the light reflection layer, and a front surface on which agroup of convex cylindrical lenses are arranged in parallel, thelenticular sheet having a surface located opposite to the lens unit,wherein: the light diffusion layer, the adhesion layer or the adhesivelayer, the light reflection layer and the lenticular sheet are providedin this order from an incidence side of the illumination light; at thelenticular sheet, on boundaries between adjacent unit lenses, a tangentline at a valley portion of any adjacent two of the unit lenses fallswithin a range of 35 to 60°; the light reflection layer includes openingportions which are formed therein to correspond to the unit lenses,respectively; and the adhesion layer or the adhesive layer is thinnerthan the light reflection layer.
 20. The optical sheet according toclaim 19, wherein the opening portions are formed of air layers.
 21. Theoptical sheet according to claim 19, wherein the opening portions areformed of material having a lower refractive index than that of thelenticular sheet.
 22. The optical sheet according to claim 19, whereinthe adhesion layer or the adhesive layer is any of ultraviolet curingresin layer, a pressure sensitive adhesive layer and a thermosensitiveadhesive layer.
 23. The optical sheet according to claim 19, wherein theadhesion layer or the adhesive layer contains light diffusion fineparticles.
 24. The optical sheet according to claim 19, wherein thelight reflection layer is formed of any of white ink, metallic foil anda metallized layer.
 25. The optical sheet according to claim 19, whereinthe lens sheet is a monolithic compact formed by press molding orextrusion molding using a thermoplastic resin.
 26. The optical sheetaccording to claim 19, wherein the lens sheet has a laminated structurein which the unit lenses are formed of hardened material of radiationhardening resin, and are polymerizing-adhered onto a surface of a basematerial sheet.
 27. The optical sheet according to claim 19, furthercomprising a light diffusion layer which is formed of a sheet or filmhaving light diffusion characteristics, on the emission surface side ofthe optical sheet.
 28. The optical sheet according to claim 19, furthercomprising a reflective polarization split film on the emission surfaceside of the optical sheet.
 29. A backlight unit for a display comprisingat least a direct-type light source and the optical sheet according toclaim 19, on a back surface of an image display element specifying adisplay image.
 30. A backlight unit for a display comprising at least asurface light source and the optical sheet according to claim 19, on aback surface of an image display element specifying a display image, thesurface light source comprising an edge-light type light source and awaveguide.
 31. A display comprising: an image display element whichcomprises a liquid crystal display element specifying a display image inaccordance with transmission of light or shutting out of light in unitsof one pixel; a light source which comprises a cold-cathode tube or anLED; and the optical sheet according to claim
 19. 32. An optical sheetfor use in illumination light control in a backlight unit for a display,comprising: a lens sheet including a lens unit in which a group ofconvex cylindrical lenses or triangular prisms are formed in parallelwith each other, the lens sheet having a surface located opposite to thelens unit, wherein: light reflection parts are provided at areas of thesurface of the lens sheet, which include boundaries between adjacentones of unit lenses or unit prisms (or lower portions of valley portionsof adjacent ones of unit lenses or unit prisms) which are included inthe lens units, light transmission parts are provided at the other areasof the surface of the lens sheet; and the light reflection parts arearranged in a stripe manner to have convex portions at the surfaceopposite to the lens unit, the convex portions being arranged tocorrespond to the unit lenses of the convex cylindrical lenses,respectively.
 33. The optical sheet according to claim 32, wherein thelight transmission parts are not flat, and have surfaces in which convexor concave portions are formed.
 34. The optical sheet according to claim33, wherein the light transmission parts contain at least convex orconcave cylindrical lenses formed therein.
 35. The optical sheetaccording to claim 32, wherein the lens sheet is a monolithic compactformed by press molding or extrusion molding using a thermoplasticresin.
 36. The optical sheet according to claim 32, wherein the lenssheet has a laminated structure in which the lens unit is formed on bothsurfaces of a light-transmission base material formed in the shape of asheet.
 37. The optical sheet according to claim 32, wherein each of thelight reflection parts is formed by applying formation or transferringformation of an ink layer formed by dispersively mixing filler metal, orlaminating formation of metallic foil.
 38. An optical sheet for use inillumination light control in a backlight unit for a display,comprising: a light diffusion layer which diffuses illumination lighttoward an emission surface side of the light diffusion layer, which is anon-incidence surface side thereof; an adhesion layer or an adhesivelayer; a light reflection layer which is adhered to the light diffusionlayer by the adhesion layer or the adhesive layer, which has a frontsurface extending along the emission surface side of the light diffusionlayer, and having a high reflectivity with respect to the emissionsurface side of the light reflection layer, and which reflects the lightdiffused by the light diffusion layer toward the light diffusion layer;and a lens sheet having a flat reverse surface fixed to the othersurface of the light reflection layer, and a front surface on which agroup of convex cylindrical lenses or triangular prisms are arranged inparallel, wherein: the light diffusion layer, the adhesion layer or theadhesive layer, the light reflection layer and the lens sheet areprovided in this order from an incidence side of the illumination light;the light reflection layer is striped to have convex portions at thesurface located opposite to the lens unit, the convex portions beingarranged to correspond to the unit lenses of the convex cylindricallenses or the triangular prisms, respectively; the light reflectionlayer includes opening portions which are formed and arranged tocorrespond to the unit lenses, respectively; and the adhesion layer orthe adhesive layer is thinner than the light reflection layer.
 39. Theoptical sheet according to claim 38, wherein the adhesion layer or theadhesive layer is any of ultraviolet curing resin layer, a pressuresensitive adhesive layer or a thermosensitive adhesive layer.
 40. Theoptical sheet according to claim 38, wherein the adhesion layer or theadhesive layer contains light diffusion fine particles.
 41. The opticalsheet according to claim 38, wherein the light reflection layer isformed of any of white ink, metallic foil and a metallized layer. 42.The optical sheet according to claim 38, wherein the lens sheet is amonolithic compact formed by press molding or extrusion molding using athermoplastic resin.
 43. The optical sheet according to claim 38,wherein the lens sheet has a laminated structure in which the unitlenses are formed of hardened material of radiation hardening resin, andare polymerizing-adhered onto a surface of a base material sheet. 44.The optical sheet according to claim 38, further comprising a lightdiffusion layer which is formed of a sheet or film having lightdiffusion characteristics, on the emission surface side of the opticalsheet.
 45. The optical sheet according to claim 38, further comprising areflective polarization split film on the emission surface side of theoptical sheet.
 46. A backlight unit for a display comprising at least adirect-type light source and the optical sheet according to claim 38, ona back surface of an image display element specifying a display image.47. A backlight unit for a display comprising at least a surface lightsource and the optical sheet according to claim 38, on a back surface ofan image display element specifying a display image, the surface lightsource comprising an edge-light type light source and a waveguide.
 48. Adisplay comprising: an image display element which comprises a liquidcrystal display element specifying a display image in accordance withtransmission of light or shutting out of light in units of one pixel; alight source which comprises a cold-cathode tube or an LED; and theoptical sheet according to claim
 38. 49. An optical sheet for use inillumination light control in a backlight unit for a display,comprising: a light diffusion layer which is provided in the shape of apattern, and diffuses illumination light toward an emission surface sideof the light diffusion layer, which is a non-incidence surface sidethereof; an adhesion layer or an adhesive layer; a light reflectionlayer which is adhered to the light diffusion layer by the adhesionlayer or the adhesive layer, which has a front surface extending alongthe emission surface side of the light diffusion layer, and having ahigh reflectivity with respect to the emission surface side of the lightreflection layer, and which reflects the light diffused by the lightdiffusion layer toward the light diffusion layer; and a lens sheetincluding a lens unit having a flat reverse surface fixed to the othersurface of the light reflection layer, and a front surface on which agroup of convex lenses or triangular prisms are arranged in parallel,the lens sheet having a surface located opposite to the lens unit,wherein: the light diffusion layer, the adhesion layer or the adhesivelayer, the light reflection layer and the lens sheet are provided inthis order from an incidence side of the illumination light; the lightreflection layer includes opening portions which are formed therein tocorrespond to unit lenses, respectively; the opening portions are formedof material having a lower refractive index than that of the lens sheet;and the adhesion layer or the adhesive layer is thinner than the lightreflection layer.
 50. The optical sheet according to claim 49, whereinthe light reflection layer is formed by applying formation ortransferring formation of an ink layer formed by dispersively mixingfiller metal, or laminating formation of metallic foil.
 51. An opticalsheet for use in illumination light control in a backlight unit for adisplay, comprising: a light diffusion layer which is provided in theshape of a pattern, and diffuses illumination light toward an emissionsurface side of the light diffusion layer, which is a non-incidencesurface side thereof; an adhesion layer or an adhesive layer; and a lenssheet including a light reflection layer which is adhered to the lightdiffusion layer by the adhesion layer or the adhesive layer, which has afront surface extending along the emission surface side of the lightdiffusion layer, and having a high reflectivity with respect to theemission surface side of the light reflection layer, and which reflectsthe light diffused by the light diffusion layer toward the lightdiffusion layer, wherein: the lens sheet has a flat reverse surfacefixed to the other surface of the light reflection layer, and a frontsurface on which a group of convex lenses or triangular prisms arearranged in parallel; the following relationship is satisfied:P≦A+2*TB*tan α where TB is a distance between a valley portion ofconcave and convex portions of the lens unit and the surface locatedopposite to the lens unit, A is a width of each of the lighttransmission parts, P is a pitch of arrangement of the convex lenses orthe triangular prisms, and α is a critical angle at an interface betweenthe light transmission parts and the lens sheet; and the adhesion layeror the adhesive layer is thinner than the light reflection layer. 52.The optical sheet according to claim 51, wherein: the followingrelationships are satisfied:0.3<TL/P<0.60.3<TB/P<1.00.3 <A/P<0.6 where TL is a height of the valley portion of the concaveand convex portions of the lens unit, TB is the distance between thevalley portion of the concave and convex portions and the surfacelocated opposite to the lens unit, A is the width of said each lighttransmission part, and the P is the pitch of arrangement of the convexlenses or the triangular prisms; and the adhesion layer or the adhesivelayer is thinner than the light reflection layer.
 53. The optical sheetaccording to claim 49, wherein the opening portions are formed of airlayers.
 54. The optical sheet according to claim 51, wherein the lightreflection layer includes opening portions which are formed therein tocorrespond to unit lenses, respectively and the opening portions areformed of material having a lower refractive index than that of the lenssheet.
 55. The optical sheet according to claim 49, wherein the adhesionlayer or the adhesive layer is any of ultraviolet curing resin layer, apressure sensitive adhesive layer and a thermosensitive adhesive layer.56. The optical sheet according to claim 49, wherein the adhesion layeror the adhesive layer contains light diffusion fine particles.
 57. Theoptical sheet according to claim 49, wherein the light reflection layeris formed of any of white ink, metallic foil and a metallized layer. 58.The optical sheet according to claim 49, wherein the lens sheet is amonolithic compact formed by press molding or extrusion molding using athermoplastic resin.
 59. The optical sheet according to claim 49,wherein the lens sheet has a laminated structure in which the unitlenses are formed of hardened material of radiation hardening resin, andare polymerizing-adhered onto a surface of a base material sheet. 60.The optical sheet according to claim 49, further comprising a lightdiffusion layer which is formed of a sheet or film having lightdiffusion characteristics, on the emission surface side of the opticalsheet.
 61. The optical sheet according to claim 49, further comprising areflective polarization split film on the emission surface side of theoptical sheet.
 62. A backlight unit for a display comprising at least adirect-type light source and the optical sheet according to claim 49, ona back surface of an image display element specifying a display image.63. A backlight unit for a display comprising at least a surface lightsource and the optical sheet according to claim 49, on a back surface ofan image display element specifying a display image, the surface lightsource comprising an edge-light type light source and a waveguide.
 64. Adisplay comprising: an image display element which comprises a liquidcrystal display element specifying a display image in accordance withtransmission of light or shutting out of light in units of one pixel; alight source which comprises a cold-cathode tube or an LED; and theoptical sheet according to claim
 49. 65. An optical sheet for use inillumination light control in a backlight unit for a display,comprising: a light diffusion layer which diffuses illumination lighttoward an emission surface side of the light diffusion layer, which is anon-incidence surface side thereof; an adhesion layer or an adhesivelayer; a light reflection layer which is formed in the shape of apattern comprising pattern portions arranged at regular intervals, andwhich is adhered to the light diffusion layer by the adhesion layer orthe adhesive layer, which has a front surface extending along theemission surface side of the light diffusion layer, and having a highreflectivity with respect to the emission surface side of the lightreflection layer, and which reflects the light diffused by the lightdiffusion layer toward the light diffusion layer; and a lenticular sheetincluding a lens unit having a flat reverse surface fixed to the othersurface of the light reflection layer, and a front surface on which agroup of convex cylindrical lenses are arranged in parallel, thelenticular sheet having a surface located opposite to the lens unit;wherein: the light diffusion layer, the adhesion layer or the adhesivelayer, the light reflection layer and the lenticular sheet are providedin this order from an incidence side of the illumination light; thelight reflection layer includes opening portions which are formedtherein and arranged to correspond to unit lenses, respectively, andwhich are formed of material having a lower refractive index than thatof the lens sheet; and the adhesion layer or the adhesive layer isthinner than the light reflection layer.
 66. The optical sheet accordingto claim 65, wherein: the group of convex cylindrical lenses arearranged in parallel at the lens unit, and the lenticular sheet has thesurface located opposite to the lens unit; light reflection parts areprovided at areas of the surface of the lenticular sheet, which areclose to a focal point of the lens unit, and light transmission partsare provided at the other areas of the surface of the lenticular sheet;and the light transmission parts have surfaces which are not flat, andin which convex or concave portions are formed.
 67. The optical sheetaccording to claim 66, wherein at the light transmission parts, at leastconvex or concave cylindrical lenses are formed.
 68. The optical sheetaccording to claim 65, wherein the lens sheet is a monolithic compactformed by press molding or extrusion molding using a thermoplasticresin.
 69. The optical sheet according to claim 65, wherein each of thelight reflection parts is formed by applying formation or transferringformation of an ink layer formed by dispersively mixing filler metal, orlaminating formation of metallic foil.
 70. The optical sheet accordingto claim 65, wherein the adhesion layer or the adhesive layer is any ofultraviolet curing resin layer, a pressure sensitive adhesive layer or athermosensitive adhesive layer.
 71. The optical sheet according to claim65, wherein the adhesion layer or the adhesive layer contains lightdiffusion fine particles.
 72. The optical sheet according to claim 65,wherein the light reflection layer is formed of any of white ink,metallic foil and a metallized layer.
 73. The optical sheet according toclaim 65, wherein the lens sheet is a monolithic compact formed by pressmolding or extrusion molding using a thermoplastic resin.
 74. Theoptical sheet according to claim 65, wherein the lens sheet has alaminated structure in which the unit lenses are formed of hardenedmaterial of radiation hardening resin, and are polymerizing-adhered ontoa surface of the optical sheet.
 75. The optical sheet according to claim65, further comprising a light diffusion layer which is formed of asheet or film having light diffusion characteristics, on the emissionsurface side of the optical sheet,
 76. The optical sheet according toclaim 65, further comprising a reflective polarization split film on theemission surface side of the optical sheet.
 77. An optical sheet for usein illumination light control in a backlight unit for a display,comprising: a light diffusion layer which diffuses illumination lighttoward an emission surface side of the light diffusion layer, which is anon-incidence surface side thereof; an adhesion layer or an adhesivelayer; a light reflection layer which is adhered to the light diffusionlayer by the adhesion layer or the adhesive layer, which has a frontsurface extending along the emission surface side of the light diffusionlayer, and having a high reflectivity with respect to the emissionsurface side of the light reflection layer, and which reflects the lightdiffused by the light diffusion layer toward the light diffusion layer;and a lens sheet having a flat reverse surface fixed to the othersurface of the light reflection layer, and a front surface on which aplurality of unit lenses are provided, wherein: the light diffusionlayer, the adhesion layer or the adhesive layer, the light reflectionlayer and the lens sheet are provided in this order from an incidenceside of the illumination light; and the light reflection layer includesopening portions which are formed therein in positions corresponding tothose of the unit lenses, respectively, and has no side robe.
 78. Abacklight unit for a display comprising at least a direct-type lightsource and the optical sheet according to claim 65, on a back surface ofan image display element specifying a display image.
 79. A backlightunit for a display comprising at least a surface light source and theoptical sheet according to claim 65, on a back surface of an imagedisplay element specifying a display image, the surface light sourcecomprising an edge-light type light source and a waveguide.
 80. Adisplay comprising: an image display element which comprises a liquidcrystal display element specifying a display image in accordance withtransmission/prevention of light-transmittance in units of one pixel; alight source which comprises a cold-cathode tube or an LED; and theoptical sheet according to claim
 65. 81. An optical sheet for use inillumination light control in a backlight unit for a display,comprising: a lens sheet including a lens unit comprising a group ofconvex cylindrical lenses which are arranged in parallel, the lens sheethaving a surface located opposite to the lens unit, wherein: lightreflection parts are provided at areas of the surface of the lens sheet,which are close to a focal point of the lens unit; light transmissionparts are provided at the other areas of the surface of the lens sheet;and the light reflection parts are arranged in a stripe manner tocorrespond to unit lenses of the convex cylindrical lenses, and haveconvex portions at the surface located opposite to the lens unit. 82.The optical sheet according to claim 81, wherein the light transmissionparts have surfaces which are not flat, and in which convex or concaveportions are formed.
 83. The optical sheet according to claim 82,wherein the light transmission parts contain at least convex or concavecylindrical lenses formed therein.
 84. The optical sheet according toclaim 81, wherein the lens sheet is a monolithic compact formed by pressmolding or extrusion molding using a thermoplastic resin.
 85. Theoptical sheet according to claim 81, wherein the lens sheet has alaminated structure in which the lens unit is formed on both surfaces ofa light-transmission base material formed in the shape of a sheet. 86.The optical sheet according to claim 81, wherein each of the lightreflection parts is formed by applying formation or transferringformation of an ink layer formed by dispersively mixing filler metal, orlaminating formation of metallic foil.
 87. An optical sheet for use inillumination light control in a backlight unit for a display,comprising: a light diffusion layer which diffuses illumination lighttoward an emission surface side of the light diffusion layer, which is anon-incidence surface side thereof; an adhesion layer or an adhesivelayer; a light reflection layer which is adhered to the light diffusionlayer by the adhesion layer or the adhesive layer, which has a frontsurface extending along the emission surface side of the light diffusionlayer, and having a high reflectivity with respect to the emissionsurface side of the light reflection layer, and which reflects the lightdiffused by the light diffusion layer toward the light diffusion layer;and a lens sheet including a lens unit having a flat reverse surfacefixed to the other surface of the light reflection layer, and a frontsurface on which a group of convex cylindrical lenses are arranged inparallel, the lens sheet having a surface located opposite to the lensunit, wherein: the light diffusion layer, the adhesion layer or theadhesive layer, the light reflection layer and the lens sheet areprovided in this order from an incidence side of the illumination light;the light reflection layer is striped to have convex portions at thesurface on the side opposite to the lens unit in positions correspondingto those of unit lenses of the convex cylindrical lenses, respectively;the light reflection layer includes opening portions which are formed tocorrespond to the unit lenses, respectively; and the adhesion layer orthe adhesive layer is thinner than the light reflection layer.
 88. Theoptical sheet according to claim 87, wherein the adhesion layer or theadhesive layer is any of ultraviolet curing resin layer, a pressuresensitive adhesive layer and a thermosensitive adhesive layer.
 89. Theoptical sheet according to claim 87, wherein the adhesion layer or theadhesive layer contains light diffusion fine particles.
 90. The opticalsheet according to claim 87, wherein the light reflection layer isformed of any of white ink, metallic foil and a metallized layer. 91.The optical sheet according to claim 87, wherein the lens sheet is amonolithic compact formed by press molding or extrusion molding using athermoplastic resin.
 92. The optical sheet according to claim 87,wherein the lens sheet has a laminated structure in which the unitlenses are formed of hardened material of radiation hardening resin, andare polymerizing-adhered onto a surface of a base material sheet. 93.The optical sheet according to claim 87, further comprising a lightdiffusion layer which is formed of a sheet or film having lightdiffusion characteristics, on the emission surface side of the opticalsheet.
 94. The optical sheet according to claim 87, further comprising areflective polarization split film on the emission surface side of theoptical sheet.
 95. A backlight unit for a display comprising at least adirect-type light source and the optical sheet according to claim 87, ona back surface of an image display element specifying a display image.96. A backlight unit for a display comprising at least a surface lightsource and the optical sheet according to claim 87, on a back surface ofan image display element specifying a display image, the surface lightsource comprising an edge-light type light source and a waveguide.
 97. Adisplay comprising: an image display element which comprises a liquidcrystal display element specifying a display image in accordance withtransmission/prevention of light-transmittance in units of one pixel; alight source which comprises a cold-cathode tube or an LED; and theoptical sheet according to claim 87.